1. Field of the Invention
The present invention relates to a base unit for use in a motor and a disk drive apparatus.
2. Description of the Related Art
Conventionally, a disk drive apparatus such as a hard disk drive apparatus or the like is equipped with a spindle motor for rotating a disk. The disk drive apparatus includes a disk, a housing, a stator, a FPC (Flexible Printed Circuit), and so forth. The housing includes a cover member, a base member, and so forth.
In recent years, the disk drive apparatus is required to become smaller in height and size. Particularly, in order to further reduce the height of a 2.5 inch disk drive apparatus of 7 mm thickness which is used in small-size disk drive apparatuses, it is necessary to reduce the thickness of a housing or a motor arranged within the housing. In general, the motor includes a rotor hub, a coil, a stator core, a wiring substrate, a base member, etc. When assembling the motor, these components are arranged to axially overlap with one another. For the sake of reducing the thickness of the motor, these components need to be made thin. However, if an attempt is made to reduce the overall height of the motor by reducing the turn number of the coils or the lamination number of the stator core, the magnetic fluxes generated in the stator during the operation of the motor are reduced such that the torque constant is reduced. It is therefore impossible to obtain the torque required in rotating the disk attached to the rotor hub.
In order to reduce the height of the motor, it is therefore necessary to reduce the thickness of the base member, among the components of the motor, which occupies a large proportion in the axial dimension of the motor. However, if the base member is merely made thin, the rigidity of the base member is reduced to a great extent. As a result, if a shock or force is applied from the outside to the base member, it is likely that the base member is broken and that the disk arranged within the housing is damaged.
Accordingly, a demand has existed for a structure capable of obtaining the rigidity of the base member while reducing the overall height of the motor.